In UMTS/3G (Universal Mobile Telecommunication System, Third generation) mobile networks, RNC (Radio Network Controller) and ATM (Asynchronous Transfer Mode) module network elements may be implemented using a concept which has separate switching units, for instance AAL (ATM Adaptation Layer, such as AAL2 ATM Adaptation Layer type 2) switching units, and separate DSP (Digital Signal Processor) processor units. A DSP is designed for signal and data handling, resembling an ordinary microprocessor. AAL2 switching units are used for demultiplexing and multiplexing AAL2 type of traffic from normal N_cid format to AAL2 1_cid format. N_cid means that one ATM cell contains several AAL2 microcells. 1_cid means that ATM cells contain only one AAL2 microcell. The basic switching function is the functionality when received N_cid is demultiplexed into 1_cids, and 1_cid, received in other direction, is multiplexed with other 1_cids to specific N_cid. N_cid is always received from, or sent to the network and 1_cid is an internal format between AAL2 switching units and between AAL2 unit and DSP processor unit. The above described type of network elements is merely presented as an example. The invention can be implemented in any type of network elements.
FIG. 4 illustrates the switching topologies in two typical switching cases. The upper part shows a first typical switching case, whereas the lower part shows another typical switching case. In FIG. 4 and the other Figures, several signal processing units such as NIU (Network Interface Unit) are shown.
It is obvious from FIG. 4 that the ATM module switching case (upper part) contains only three ATM-level connections whereas the RNC switching case needs four ATM-level cross-connections. These connections are currently handled under the leg concept schematically shown in FIG. 5. As illustrated in FIG. 5, ATM connections are provided for interconnecting the network elements in such a manner that legs are formed which end between the MDC and right-hand AAL2 element and are connected by means of a leg connector for finally providing a through switch connection.
The requirements for handling the connection are high and the creation of an ATM connection is quite complex due to Quality of Service (QoS) requirements, hardware structure and so on. For making one ATM connection in the ATM level, a minimum of four messages across the computers inside the switching system is required. In other structures, it may be possible to implement such an ATM connection with two messages. However, in basic cases four cross-connections per one through switch connection are created.
The number of created ATM connections will advantageously be reduced when providing N_cid connections because one N_cid contains several connections. For instance, an N_cid VCC (Virtual Channel Connection) is created only once for 248 N_cids (in optimal situation). N_cid is terminated in AAL2 switching unit and there are for each cid one ATM layer level VCC connection. The VCC connection needs to be created every time when a new AAL2 connection is created. The same applies for the case of deletion of connections.
In the following, some problems related to these connection setup requirements are discussed. The ATM connection control needs a very fast data management tool to handle all the termination point and cross-connection object setups and deletions. Further, the number of messages required and/or the number of all connection setup/deletions per unit time such as 1 second is very high. MXU's SAR (Multiplexer Unit's Segmentation and Reassembly) and CPU (Central processing unit) processing performance is required to be very high to be adequate for handling the data streams. Moreover, a heavy CAC (Connection Admission Control) load occurs as each setup goes through CAC in several points (corresponding to hardware (HW)).
The invention relates, among others, to Virtual Channel and Virtual Path technology. A virtual channel (VC) designates a unidirectional transport of ATM cells associated by a common unique identifier value. A virtual channel connection (VPC) is a concatenation of virtual channel links that forms an ATM connection between a transmitting party and a receiving party, and in which both virtual path and virtual channel identifiers are used. A virtual path (VP) means a unidirectional transport of ATM cells that are associated by a common identifier value. A virtual path connection (VPC) is a concatenation of virtual path links that extends between the point where the virtual channel identifier values are assigned and the point where those virtual values are translated or removed.